.\" This is -*-nroff-*-
.\" XXX standard disclaimer belongs here....
.\" $Header: /usr/local/cvsroot/postgres95/src/man/postmaster.1,v 1.3 1997/01/26 15:32:28 scrappy Exp $
.TH POSTMASTER UNIX 11/05/95 PostgreSQL PostgreSQL
.SH "NAME"
postmaster \(em run the Postgres postmaster
.SH "SYNOPSIS"
.BR "postmaster"
[\c
.BR "-B"
n_buffers]
[\c
.BR "-D"
data_dir]
[\c
.BR "-S" \c
]
[\c
.BR "-a"
system]
.br
.in +5n
[\c
.BR "-b"
backend_pathname]
[\c
.BR "-d"
[debug_level]]
[\c
.BR "-n" \c
]
[\c
.BR "-e" \c
]
.br
[\c
.BR "-o"
backend_options]
[\c
.BR "-p"
port]
[\c
.BR "-s" \c
]
.in -5n
.SH "DESCRIPTION"
The
.IR "postmaster"
manages the communication between frontend and backend processes, as
well as allocating the shared buffer pool and semaphores (on machines
without a test-and-set instruction).  The 
.IR postmaster
does not itself interact with the user and should be started as a
background process.
.BR "Only one postmaster should be run on a machine."
.PP
The 
.IR "postmaster"
understands the following command-line options:
.TP 5n
.BR "-B" " n_buffers"
.IR "n_buffers"
is the number of shared-memory buffers for the 
.IR "postmaster"
to allocate and manage for the backend server processes that it
starts.  This value defaults to 64.
.TP
.BR "-D" " data_dir"
Specifies the directory to use as the root of the tree of database
directories.  This directory uses the value of the environment
variable 
.SM PGDATA.
If 
.SM PGDATA
is not set, then the directory used is
.SM $POSTGRESHOME\c
/data.  If neither environment variable is set and this command-line
option is not specified, the default directory that was
set at compile-time is used.
.TP
.BR "-S"
Specifies that the
.IR "postmaster"
process should start up in silent mode.  That is, it will disassociate
from the user's (controlling) tty and start its own process group.
This should not be used in combination with debugging options because
any messages printed to standard output and standard error are 
discarded.
.TP
.BR "-a" " system"
Specifies whether or not to use the authentication system 
.IR "system"
(see 
.IR introduction (1))
for frontend applications to use in connecting to the 
.IR postmaster
process.  Specify
.IR "system"
to enable a system, or
.BI "no" "system"
to disable a system.  For example, to permit users to use
.IR Kerberos
authentication, use 
.BR "-a kerberos" ;
to deny any unauthenticated
connections, use
.BR "-a nounauth .
The default is site-specific.
.TP
.BR "-b" " backend_pathname"
.IR "backend_pathname"
is the full pathname of the Postgres backend server executable file that
the
.IR "postmaster"
will invoke when it receives a connection from a frontend application.
If this option is not used, then the 
.IR postmaster
tries to find this executable file in the directory in which its own
executable is located (this is done by looking at the pathname under
which the
.IR "postmaster"
was invoked.  If no pathname was specified, then the
.SM PATH
environment variable is searched for an executable named
\*(lqpostgres\*(rq).
.TP
.BR "-d" " [debug_level]"
The optional argument
.IR debug_level
determines the amount of debugging output the backend servers will
produce.
If
.I debug_level
is one, the postmaster will trace all connection traffic,
and nothing else.
For levels two and higher,
debugging is turned on in the backend process and the postmaster
displays more information,
including the backend environment and process traffic.
Note that if no file is specified for backend servers to
send their debugging output then this output will appear on the
controlling tty of their parent 
.IR postmaster .
.TP
.BR "-n" ", " "-s"
The
.IR "-s" " and " "-n"
options control the behavior of the
.IR "postmaster"
when a backend dies abnormally.  \fBNeither option is intended for use in
ordinary operation\fP.
.IP
The ordinary strategy for this situation is to notify all other
backends that they must terminate and then reinitialize the shared
memory and semaphores.  This is because an errant backend could have
corrupted some shared state before terminating.
.IP
If the
.IR "-s"
option is supplied, then the
.IR "postmaster"
will stop all other backend processes by sending the signal
.SM SIGSTOP,
but will not cause them to terminate.  This permits system programmers
to collect core dumps from all backend processes by hand.
.IP
If the
.IR "-n"
option is supplied, then the
.IR "postmaster"
does not reinitialize shared data structures.  A knowledgable system
programmer can then use the
.IR shmemdoc
program to examine shared memory and semaphore state.
.TP
.BR "-e"
The
.IR "-e"
option controls how dates are input to and output from the database.
.IP
If the
.IR "-e"
option is supplied, then all dates passed to and from the frontend
processes will be assumed to be in
.IR "European"
format ie.
.IR "DD-MM-YYYY"
otherwise dates are input and output in
.IR "American"
format ie.
.IR "MM-DD-YYYY"
.TP
.BR "-o" " backend_options"
The 
.IR postgres (1)
options specified in
.IR "backend_options"
are passed to all backend server processes started by this
.IR postmaster .
If the option string contains any spaces, the entire string must be
quoted.
.TP
.BR "-p" " port"
Specifies the Internet TCP port on which the
.IR postmaster
is to listen for connections from frontend applications.  Defaults to
5432, or the value of the 
.SM PGPORT 
environment variable (if set).  If you specify a port other than the
default port then all frontend application users must specify the same
port (using command-line options or
.SM PGPORT\c
) when starting any libpq application, including psql.
.SH "WARNINGS"
If at all possible,
.BR "do not"
use
.SM SIGKILL
when killing the
.IR "postmaster" "."
.SM SIGHUP,
.SM SIGINT,
or
.SM SIGTERM
(the default signal for 
.IR "kill" "(1))"
should be used instead.  Hence, avoid
.nf
kill -KILL
.fi
or its alternative form
.nf
kill -9
.fi
as this will prevent the
.IR postmaster
from freeing the system resources (e.g., shared memory and semaphores)
that it holds before dying.  This prevents you from having to deal with
the problem with
.IR shmat (2)
described below.
.SH "EXAMPLES"
.nf

# start postmaster using default values
nohup postmaster >logfile 2>&1 &

.fi
This command will start up 
.IR "postmaster"
on the default port (5432) and will search 
.SM $PATH
to find an executable file called \*(lqpostgres\*(rq.  This is the
simplest and most common way to start the
.IR "postmaster" .
.nf

# start with specific port and executable name
nohup postmaster -p -b /usr/postgres/bin/postgres &

.fi
This command will start up a 
.IR "postmaster"
communicating through the port 1234, and will attempt to use the
backend located at \*(lq/usr/postgres/bin/postgres\*(rq.  In order to
connect to this
.IR "postmaster"
using psql, you would need to either
specify
.BR "-p 1234"
on the 
.IR "psql"
command-line or set the environment variable
.SM PGPORT
to 1234.
.SH "SEE ALSO"
ipcs(1),
ipcrm(1),
ipcclean(1),
psql(1), 
postgres(1), 
.SH "DIAGNOSTICS"
.TP
.BR "FindBackend: could not find a backend to execute..."
If you see this message, you do not have the 
.IR "postgres"
executable in your path.  Add the directoy in which postgres resides to
your path.
.TP
.BR "semget: No space left on device"
If you see this message, you should run the
.IR "ipcclean"
command.  After doing this, try starting the
.IR "postmaster"
again.  If this still doesn't work, you probably need to configure
your kernel for shared memory and semaphores as described in the
installation notes.  If you run multiple 
.IR postmaster s
on a single host, or have reduced the shared memory and semaphore
parameters from the defaults in the generic kernel, you may have to 
go back and increase the shared memory and semaphores configured 
into your kernel.
.TP
.BR "StreamServerPort: cannot bind to port"
If you see this message, you should be certain that there is no other 
.IR "postmaster"
process already running.  The easiest way to determine this is by
using the command
.nf
ps -ax | grep postmaster
.fi
on BSD-based systems
.nf
ps -e | grep postmast
.fi
(the equivalent syntax is on System V-like or POSIX-compliant systems such as HP-UX).  If you 
are sure that no other
.IR "postmaster"
processes are running and you still get this error, try specifying a
different port using the
.BR "-p"
option.  You may also get this error if you terminate the
.IR "postmaster"
and immediately restart it using the same port; in this case, you must
simply wait a few seconds until the operating system closes the port
before trying again.  Finally, you may get this error if you specify
a port number that your operating system considers to be reserved.
For example, many versions of Unix consider port numbers under 1024 to
be \*(lqtrusted\*(rq and only permit the Unix superuser to access them.
.TP
.BR "IpcMemoryAttach: shmat() failed: Permission denied"
A likely explanation is that another user attempted to start a
.IR "postmaster"
process on the same port which acquired shared resources and then 
died.  Since Postgres shared memory keys are based on the port number 
assigned to the
.IR "postmaster" ,
such conflicts are likely if there is more than one installation on 
a single host.  If there are no other
.IR "postmaster"
processes currently running (see above), run
.IR "ipcclean"
and try again.  If other 
.IR "postmaster" s
are running, you will have to find the owners of those processes to
coordinate the assignment of port numbers and/or removal of unused
shared memory segments.
